1. Field of the Invention
The present invention relates to a method for manufacturing semiconductor chips from a semiconductor wafer.
2. Discussion of the Related Art
The manufacturing of semiconductor chips especially comprises steps during which components and interconnect metallizations are formed inside and on top of a semiconductor wafer, followed by a step during which the wafer is cut into individual chips, for example, by means of a saw. Various individual chip testing steps are generally provided after the cutting.
FIGS. 1A, 1B and 2A, 2B schematically illustrate steps of a method for cutting a semiconductor wafer 10 into individual chips by means of a saw. FIGS. 1A and 2A are top views and FIGS. 1B and 2B respectively are cross-section views along planes B-B of FIGS. 1A and 2A.
FIGS. 1A and 1B illustrate an initial step in which wafer 10 is arranged on a surface of an adhesive film 12 stretched on a support frame 14. Generally, wafer 10 has an approximately round shape and frame 14 has a round inner contour with a diameter greater than the diameter of wafer 10. In this example, the outer contour of frame 14 has a generally approximately square shape with rounded corners and comprises location notches 16.
The specific shape of frame 14, and more specifically of its outer contour, enables to accurately position the wafer in a processing machine, for example, a sawing machine. In a given production line, frame 14 generally is an element of standard shape and dimension, used at various steps of the manufacturing during which the wafer should be maintained on a support. Thus, the various machines of a given manufacturing line are provided to receive a type of support frame 14, of given shape and dimensions.
FIGS. 2A and 2B illustrate the actual operation of cutting of wafer 10 into individual chips 18. The cutting is conventionally performed by means of a circular saw (not shown) running through the wafer along a grid of lines and columns. The cutting is performed across the entire thickness of the wafer and stops in the upper portion of adhesive film 12, without however cutting this film. It should be noted that, in practice, a semiconductor wafer comprises a much greater number of elementary chips 18 than what has been shown. It should be noted that generally, the semiconductor wafer is not perfectly circular but has a flat side, not shown, enabling to align all wafers in the same way with respect to frame 14.
After the wafer has been cut, the individual chips remain on frame 14, and other manufacturing steps may be provided, during which the cut wafer is processed in machines capable of receiving frame 14. Such steps for example are a visual inspection of the chips, a probe test, a marking of defective chips, etc. Adhesive film 12 especially enables chips 18 to remain in place during these steps and during subsequent transportations of frame 14.
In some cases, the user or the customer desires to receive the cut chips to assemble them in various electronic devices. The chips are then shipped on the support frame 14 on which they have been cut. On reception of the chips, the test and/or inspection steps may be implemented again by using equipment capable of receiving frame 14. The actual mounting of the chips, for example, their mounting on printed circuit boards, is also carried out by means of machines capable of receiving frame 14.
The different manufacturers and users of semiconductor chips do not necessarily use the same support frame standards. Now, generally, given equipment is equipped to receive frames of a single standard. Accordingly, in such a production system, a manufacturer of semiconductor chips using a given type of frame can only sell his production to users equipped to receive this type of frame.
FIGS. 3 and 4 are top views schematically showing, respectively, a frame 34 and a frame 44, corresponding to two standards much used in the art to support wafers having a 20-cm diameter (approximately 8 inches), that is, standard FF-108 and standard FF-105. Frames 34 and 44 have approximately identical general shapes but different dimensions. The general shapes of frames 34 and 44 are similar. Frame 44 has dimensions slightly smaller than the dimensions of frame 34, and in particular outer dimensions smaller than the outer dimensions of frame 34 but greater than the inner diameter of frame 34. In this example, the inner diameter of frame 44 is slightly smaller than the inner diameter of frame 34. The difference in outer dimensions especially results in that the machines capable of receiving frame 34 are not capable of receiving frame 44, and conversely.
It would be desirable for a manufacturer having equipment capable of receiving frame 34 to be able to sell his production to a user having equipment capable of receiving frame 44 (smaller than frame 34) without for one or the other of the manufacturer and of the user to have to modify his machines.